Internal combustion engines produce drive torque that is transferred to a drivetrain. The drive torque is transferred through a transmission that multiplies the drive torque by a gear ratio. Transmissions generally include multiple gear ratios through which the drive torque is transferred. Automatic transmissions automatically shift between gear ratios based on driver input and vehicle operating conditions. Hybrid powertrains typically include an electric machine and an energy storage device (ESD). In one mode, the electric machine drives the transmission using energy stored in the ESD. In another mode, the electric machine is driven by the engine to charge the ESD.
Traditional transmission control systems determine shift decisions based on vehicle speed and throttle. The shift strategy is developed based on vehicle performance, drivability and fuel economy based on anticipated driving conditions. The shift strategy also must account for engine sub-systems (e.g., variable valve timing (VVT)) and other features including, but not limited to, powertrain braking, GPS-based shifting and hybrid vehicle functions. In a hybrid powertrain, the shift control strategy must also account for electrical requirements (i.e., driving or powering the electric machine). As a result, transmission control systems, those for hybrid powertrains in particular, are more complex than desired and require significant time to calibrate.